Watercraft and exhaust structure of the watercraft

ABSTRACT

An exhaust system for a watercraft with an engine includes an upstream exhaust pipe including an end portion with an outlet, a water lock including an inner space accommodating the end portion, a downstream exhaust pipe connected to the water lock, and a flow direction diverter, such as a baffle. The upstream exhaust pipe guides exhaust gas from the engine to the end portion. The inner space of the water lock receives the exhaust gas from the outlet of the end portion. The downstream exhaust pipe exhausts the exhaust gas from the inner space to an outside of the watercraft body. The flow direction diverter changes a flow direction of the exhaust gas at the outlet to a cross direction which intersects a pipe axis of the end portion.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a watercraft including an engine, andan exhaust system for the watercraft.

2. Description of the Related Art

A water vehicle disclosed in Japanese Patent Application Publication No.2008-157217 includes an exhaust device that exhausts gas emitted from anengine to the outside of a watercraft body. The exhaust device includesa first exhaust pipe extending rearward from a side portion of theengine, a water lock having a tank shape connected to a rear end portionof the first exhaust pipe, and a second exhaust pipe which is connectedto a rear portion of the water lock and which opens at a lower portionof a rear end of the watercraft body. The interior of the water lock isdivided into an upstream area and a downstream area by a partition. Apartition pipe penetrates the partition. The rear end portion of thefirst exhaust pipe includes an inner pipe located at the upstream areain the water lock. An upstream end portion of the second exhaust pipe islocated at the downstream area in the water lock.

The exhaust gas emitted from the engine flows from an outlet of theinner pipe into the upstream area in the water lock via the firstexhaust pipe, passes the partition pipe, and flows into the downstreamarea in the water lock. The exhaust gas is then exhausted to the outsideof the watercraft body via the second exhaust pipe.

The outlet of the inner pipe disclosed in Japanese Patent ApplicationPublication No. 2008-157217 is opposed to or faces the partition in adirection along a pipe axis of the inner pipe. Thus, a portion of theexhaust gas flowing into the upstream area in the water lock from theoutlet flows straight along the pipe axis and collides with thepartition and the partition pipe. Accordingly, there is a possibilitythat turbulence occurs in the water lock. If turbulence occurs in thewater lock, it is difficult for the exhaust gas in the water lock toreach the second exhaust pipe, and the exhaust efficiency to the outsideof the watercraft body deteriorates.

SUMMARY OF THE INVENTION

In order to overcome the previously unrecognized and unsolved challengesdescribed above, a preferred embodiment of the present inventionprovides a watercraft including a watercraft body, an engine in thewatercraft body, an upstream exhaust pipe including an end portionincluding an outlet, a water lock including an inner space which housesthe end portion, a downstream exhaust pipe connected to the water lock,and a flow direction diverter. The upstream exhaust pipe, the waterlock, the downstream exhaust pipe, and the flow direction diverterdefine an exhaust system of the watercraft. The upstream exhaust pipeguides the exhaust gas from the engine to the end portion. The innerspace of the water lock receives the exhaust gas from the outlet of theend portion. The downstream exhaust pipe exhausts the exhaust gas fromthe inner space to an outside of the watercraft body. The flow directiondiverter changes a flow direction of the exhaust gas at the outlet to across direction which intersects a pipe axis of the end portion.

According to this preferred embodiment, the exhaust gas that reaches theend portion of the upstream exhaust pipe from the engine flows into theinner space of the water lock from the outlet of the end portion to thecross direction intersecting the pipe axis of the end portion. Theexhaust gas which flows into the inner space of the water lock flowsalong an inner wall of the water lock. Thus, turbulence in the waterlock is significantly reduced or prevented, the exhaust gas in the waterlock smoothly reaches the downstream exhaust pipe, and the exhaust gasis exhausted to the outside of the watercraft body. Accordingly, exhaustefficiency is improved.

In a preferred embodiment of the present invention, the end portionpenetrates an inner wall of the water lock along a pipe axis direction,and the flow direction diverter changes the flow direction of theexhaust gas to a direction along the inner wall.

According to this preferred embodiment, the exhaust gas which flows intothe inner space of the water lock from the outlet of the end portion ofthe upstream exhaust pipe flows along the inner wall of the water lock.Flow of the exhaust gas in the inner space of the water lock isaccelerated. Thus, turbulence in the water lock is further reduced orprevented, and exhaust efficiency is further improved.

In a preferred embodiment of the present invention, the outletpreferably opens radially to the outside of the upstream exhaust pipe atthe end portion. According to this preferred embodiment, the exhaust gasflows along the inner wall of the water lock. Flow of the exhaust gas inthe inner space of the water lock is accelerated. Thus, turbulence inthe water lock is further reduced or prevented, and exhaust efficiencyis further improved.

In a preferred embodiment of the present invention, the flow directiondiverter includes a baffle that blocks the exhaust gas which reaches theend portion to change the flow direction of the exhaust gas.

According to this preferred embodiment, the exhaust gas which reachesthe end portion of the upstream exhaust pipe cannot flow straight alongthe pipe axis of the end portion due to the baffle. Thus, the flowdirection of the exhaust gas at the outlet of the end portion is changedto the cross direction.

In a preferred embodiment of the present invention, the watercraftfurther includes a fastener that fastens the baffle to the end portion.

According to this preferred embodiment, the baffle is stabilized bybeing fastened to the end portion of the upstream exhaust pipe, andblocks the exhaust gas which reaches the end portion to change the flowdirection of the exhaust gas.

In a preferred embodiment of the present invention, the fastenerincludes three or more fasteners.

According to this preferred embodiment, the baffle is fastened to theend portion of the upstream exhaust pipe by the three or more fasteners.Thus, the baffle is further stabilized.

In a preferred embodiment of the present invention, the watercraftfurther includes a drain pipe surrounding the end portion. A flowpassage is defined between the drain pipe and the end portion, andguides engine cooling water to the inner space.

According to this preferred embodiment, cooling water which flows intothe inner space of the water lock from the flow passage smoothly reachesthe downstream exhaust pipe and is drained to the outside of thewatercraft body from the downstream exhaust pipe by being carried by theexhaust gas flowing along the inner wall of the water lock. Thus, bothexhaust efficiency and cooling water drainage efficiency is improved,and turbulence in the water lock is significantly reduced or prevented,as discussed above. For example, spray of cooling water stirred by theturbulence in the water lock is significantly reduced or prevented.Thus, spray flowing backward in the upstream exhaust pipe byinfiltrating into the upstream exhaust pipe from the outlet issignificantly reduced or prevented.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a watercraft according to a preferredembodiment of the present invention.

FIG. 2 is a sectional view of an exhaust system of the watercraft cutalong a plane extending in the up-down and front-rear directions.

FIG. 3 is a perspective view of an end portion of an upstream exhaustpipe of the exhaust system.

FIG. 4 is a perspective view of an end portion of an upstream exhaustpipe according to a first modification of a preferred embodiment of thepresent invention.

FIG. 5 is a perspective view of an end portion of an upstream exhaustpipe according to a second modification of a preferred embodiment of thepresent invention.

FIG. 6 is a sectional view of an exhaust system according to a thirdmodification of a preferred embodiment of the present invention cutalong a plane extending in the up-down and front-rear directions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

First Preferred Embodiment

FIG. 1 is a schematic view of a watercraft 1 according to a preferredembodiment of the present invention. A right-left direction in FIG. 1 isdefined as the front-rear direction of the watercraft 1. The left sidein FIG. 1 shows the front of the watercraft 1. A right-left direction ofthe watercraft 1 is seen when facing in the traveling direction of thewatercraft 1. Thus, the near side in a direction perpendicular to thesheet of FIG. 1 corresponds to the left of the watercraft 1, and the farside in the direction perpendicular to the sheet of FIG. 1 correspondsto the right of the watercraft 1.

The watercraft 1 includes a watercraft body 2, and an engine 3 in aninterior of the watercraft body 2. The watercraft body 2 includes a hull4 that defines a watercraft bottom, and a deck 5 located above the hull4. The watercraft body 2 is elongated in the front-rear direction. Theengine 3 is located in an engine room between the hull 4 and the deck 5in an up-down direction. The engine 3 is preferably an internalcombustion engine including a crankshaft that rotates about a crank axisextending in the front-rear direction.

The watercraft 1 of this preferred embodiment is preferably a jetpropelled watercraft, for example, and further includes a seat 6 onwhich a rider sits, a steering handle 7 that is operated to the rightand left by the rider, and a jet pump 8 mounted on a rear portion of thewatercraft body 2. The seat 6 and the steering handle 7 are located onan upper side of the watercraft body 2. A throttle lever is mounted on aright end portion of the steering handle 7. A driving force of theengine 3 is adjusted by operation of the throttle lever by the rider.

The jet pump 8 is located rearward relative to the engine 3. The jetpump 8 sucks in water from the watercraft bottom and ejects the water toan outside of the watercraft body 2 by a driving force of the engine 3.The jet pump 8 generates a thrust to propel the watercraft 1 forward.

For example, the jet pump 8 includes an intake 9 into which wateroutside the watercraft body 2 is sucked, an outlet 10 from which thewater sucked in from the intake 9 is ejected rearward, and a flowpassage 11 that guides the water sucked into the intake 9 to the outlet10. The jet pump 8 further includes a driveshaft 12 extending in thefront-rear direction, an impeller 13 and a stator vane 14 that arelocated in the flow passage 11, a nozzle 15, and a deflector 16 thatdeflects or directs water ejected rearward from the nozzle 15 to theright and left.

The intake 9 opens at the watercraft bottom, and the outlet 10 opensrearward at a location farther to the rear than the intake 9. A frontend portion of the driveshaft 12 is located in the watercraft body 2 andcoupled to the crankshaft of the engine 3 via a coupling or the like,for example. A rear end portion of the driveshaft 12 is located in theflow passage 11 and coupled to the impeller 13. The stator vane 14 islocated behind the impeller 13, and the nozzle 15 is located behind thestator vane 14. The stator vane 14 and the nozzle 15 are fixed withrespect to the flow passage 11.

The impeller 13 is rotatable in the flow passage 11 about a central axisof the driveshaft 12. The impeller 13 is driven by the engine 3 torotate about the central axis of the driveshaft 12 together with thedriveshaft 12. When the impeller 13 is driven to rotate, water outsidethe watercraft body 2 is sucked into the flow passage 11 from the intake9 and is fed from the impeller 13 to the stator vane 14. A torsionalwater flow produced by rotation of the impeller 13 is reduced andstraightened by the water fed by the impeller 13 and passing through thestator vane 14. Thus, the flow-straightened water is delivered from thestator vane 14 to the nozzle 15. The nozzle 15 preferably has a tubularor substantially tubular shape extending in the front-rear direction,and the outlet 10 is defined by a rear end portion of the nozzle 15. Thewater fed to the nozzle 15 is thus jetted rearward from the outlet 10 ofthe rear end portion of the nozzle 15.

The deflector 16 extends rearward from the nozzle 15. The deflector 16is coupled to the nozzle 15 and rotates to the right and left about adeflector axis 16A extending in the up-down direction. The deflector 16is preferably hollow. The outlet 10 of the nozzle 15 is located in thedeflector 16. The deflector 16 defines an ejection port 17 that opensrearward. The ejection port 17 is located behind the outlet 10. Waterjetted rearward from the outlet 10 penetrates through an interior of thedeflector 16 and is ejected rearward from the ejection port 17. Thedeflector 16 turns to the right and left according to an operation ofthe steering handle 7. The water that is ejected from the jet pump 8 isdirected to the right and left by the operation of the steering handle 7to steer the watercraft 1.

The watercraft 1 further includes an exhaust system 20 that exhaustsexhaust gas generated in the engine 3 to the outside of the watercraftbody 2. An exhaust port 2A is located at a rear of a left surface or aright surface of the watercraft body 2. The exhaust system 20 includesan upstream exhaust pipe 21, a water lock 22, and a downstream exhaustpipe 23. The exhaust system 20 is located in the watercraft body 2.

The upstream exhaust pipe 21 is connected to an exhaust port of acylinder of the engine 3. When there are two or more cylinders, theexhaust port of each cylinder is connected to the upstream exhaust pipe21 which joins each exhaust port and then extends rearward. The upstreamexhaust pipe 21 guides the exhaust gas from the exhaust port of theengine 3 rearward. An end portion 21A, which is located at a downstreamend of the upstream exhaust pipe 21 in a flow direction of the exhaustgas, defines a rear end portion of the upstream exhaust pipe 21. In apreferred embodiment, at least the upstream exhaust pipe 21 of theexhaust system 20 is made of metal since the exhaust gas emitted fromthe engine 3 and flowing into the upstream exhaust pipe 21 is relativelyhot.

FIG. 2 is a sectional view of the exhaust system 20 when cut along aplane extending in the up-down and front-rear directions and seen fromleft. The end portion 21A preferably has a pipe shape (for example, acircular or substantially circular pipe shape) including a pipe axis A.In a preferred embodiment, a pipe axis direction of the pipe axis Acoincides with the front-rear direction of the watercraft 1. In anotherpreferred embodiment, the end portion 21A has, for example, arectangular or substantially rectangular pipe shape having a polygonalcross section, such as a rectangular or substantially rectangular shape,when cut along a plane perpendicular to the pipe axis A. A narrowportion 21B in the middle of the end portion 21A in the front-reardirection is one step narrower than the end portion 21A. A circular orsubstantially circular opening 21C is located at a rear end of the endportion 21A. A plurality of outlets 21D are disposed on an outerperipheral surface of the end portion 21A. Each of the outlets 21Dpenetrates the end portion 21A along a radial direction R, with the pipeaxis A as a center, and opens to the outside in the radial direction R.In a preferred embodiment, the outlets 21D include, for example, four ormore outlets 21D aligned in the front-rear direction at equal orsubstantially equal intervals that define a line. In a preferredembodiment, a plurality of lines are aligned in a circumferentialdirection S about the pipe axis A on the outer peripheral surface of theend portion 21A. A plurality of lines are distributed in acircumferential direction S about the pipe axis A on the outerperipheral surface of the end portion 21A and are located rearwardrelative to the narrow portion 21B. In a preferred embodiment, theoutlet 21D includes, for example, a round or substantially round hole ora slit extending in the front-rear direction or the circumferentialdirection S. The outlet 21D may include one or more than one outlet 21D.

The exhaust system 20 further includes a baffle 25 serving as a flowdirection diverter. In a preferred embodiment, the baffle 25 preferablyhas a circular or substantially circular plate shape, for example, witha plate thickness direction that coincides with the front-reardirection. The baffle 25 is opposed to or covers the end portion 21Afrom the rear and blocks the opening 21C. The end portion 21A includesthe baffle 25 when the baffle 25 is fastened to the end portion 21A. Ina preferred embodiment, the baffle 25 is fastened to the end portion 21Aby a plurality of bolts 26, for example, that serve as fasteners. In apreferred embodiment, three bolts 26, for example, define and functionas the fasteners.

FIG. 3 is a perspective view of the end portion 21A to which the baffle25 is fastened as seen from the rear. The end portion 21A integrally andunitarily includes a ring-shaped or substantially ring-shaped flange 21Ewhich overhangs to the outside in the radial direction R from all areasin the circumferential direction S of a rear end of the end portion 21A,and a bulge 21F which bulges to the outside in the radial direction Rfrom the outer peripheral surface of the end portion 21A and whichextends forward from the flange 21E. In a preferred embodiment, thebulge 21F includes two or more bulges 21F corresponding to a number ofthe bolts 26. For example, in a preferred embodiment, three bulges 21Fare aligned in the circumferential direction S at equal or substantiallyequal intervals. The outlets 21D are deviated or offset from the bulge21F in the circumferential direction S. For example, the outlets 21D aredisposed between neighboring bulges 21F. An outer periphery 25A of thebaffle 25 overlaps with the flange 21E from the rear.

A screw portion or thread of each bolt 26 penetrates the outer periphery25A and the flange 21E from the rear and is installed in a screw hole inthe corresponding bulge 21F. The three bolts 26 are aligned in thecircumferential direction S at equal or substantially equal intervals.Thus, the baffle 25 is fastened to the end portion 21A by the threebolts 26. In this preferred embodiment, the baffle 25 is more stablethan when two or less bolts 26 are used.

The water lock 22 is located between the engine 3 and the jet pump 8 inthe front-rear direction (FIG. 1). Referring to FIG. 2, the water lock22 preferably has an elongated tank shape, for example, that extends inthe front-rear direction. The water lock 22 integrally and unitarilyincludes a cylindrical or substantially cylindrical portion 22A(hereinafter, “cylindrical portion 22A”) which extends in the front-reardirection, a rear baffle 22C which is connected to a rear end of thecylindrical portion 22A and blocks an inner space 22B of the cylindricalportion 22A from the rear, and a front baffle 22D which is connected toa front end portion of the cylindrical portion 22A and blocks the innerspace 22B from the front. Each of the rear baffle 22C and the frontbaffle 22D preferably has a circular or substantially circular plateshape. In a preferred embodiment, the rear baffle 22C is curved andbulges rearward, and the front baffle 22D is curved and bulges forward.A protruding portion 22E protruding forward is integrally and unitarilydisposed at a central or substantially central portion of the frontbaffle 22D. The protruding portion 22E preferably has a cylindrical orsubstantially cylindrical shape having a smaller outer diameter thanthat of the cylindrical portion 22A. An inner space 22F of theprotruding portion 22E communicates with the inner space 22B of thecylindrical portion 22A from the front. An entire inner space 22G of thewater lock 22 includes the inner space 22F and the inner space 22B. Anopening 22H communicating with the inner space 22F is disposed at afront end of the protruding portion 22E.

A portion of the end portion 21A of the upstream exhaust pipe 21 that islocated rearward relative to at least the narrow portion 21B is insertedinto the inner space 22F of the protruding portion 22E from the opening22H. The end portion 21A is inserted beyond the protruding portion 22Eto a front end portion of the inner space 22B of the cylindrical portion22A. For example, the end portion 21A penetrates an inner wall 221 ofthe water lock 22 of the front baffle 22D along the front-reardirection. At least the outlet 21D of the end portion 21A is located inthe inner space 22B of the cylindrical portion 22A. The end portion 21Awithin the inner space 22B is preferably coaxial with the cylindricalportion 22A and the protruding portion 22E. A flow passage 27 is definedbetween the end portion 21A and the protruding portion 22E whichsurrounds the end portion 21A. The flow passage 27 is preferablyring-shaped, extends in the front-rear direction between the end portion21A and the protruding portion 22E, and communicates with the innerspace 22B from the front.

The downstream exhaust pipe 23 includes an upstream end portion 23Aconnected to the water lock 22 by penetrating the cylindrical portion22A of the water lock 22 from above, and a downstream end portion 23B(FIG. 1) connected to the exhaust port 2A of the watercraft body 2. Thedownstream exhaust pipe 23 extends from the upstream end portion 23A tothe downstream end portion 23B. In order to prevent water from outsidethe watercraft body 2, such as seawater, from flowing backward in thedownstream exhaust pipe 23, a midway portion of the downstream exhaustpipe 23 between the upstream end portion 23A and the downstream endportion 23B is bent to extend upward and then downward (FIG. 1).

The upstream end portion 23A is located at a rear portion of the innerspace 22B of the cylindrical portion 22A. An inlet 23C which opensdownward is located at a lower end of the upstream end portion 23A. Whenthe watercraft 1 is upset or overturned and the up-down direction of thewatercraft body 2 and the exhaust system 20 is reversed, the inlet 23Cis located at a higher position than the water surface around thewatercraft body 2. Thus, water outside the watercraft body 2 that mayflow backward in the downstream exhaust pipe 23 from the exhaust port 2Aand infiltrate into the water lock 22 from the inlet 23C issignificantly reduced or prevented. The upstream end portion 23A ispreferably at a same or a substantially same position as the end portion21A of the upstream exhaust pipe 21 and the baffle 25 in the right-leftdirection of the watercraft 1 (a direction perpendicular to the sheet ofFIG. 2) and is opposed to or overlaps the end portion 21A and the baffle25 from the rear in the inner space 22B. Alternatively, the upstream endportion 23A may be located at a position deviated from the end portion21A and the baffle 25 in the right-left direction.

The exhaust system 20 further includes a drain pipe 30 and a coolingpipe 31. The drain pipe 30 preferably coaxially surrounds the endportion 21A of the upstream exhaust pipe 21 and defines a flow passage32 between the drain pipe 30 and the end portion 21A. The flow passage32 is preferably ring-shaped and extends in the front-rear directionbetween an outer circumferential surface of the end portion 21A and aninner circumferential surface of the drain pipe 30. A front end portionof the flow passage 32 is closed. The flow passage 32 communicates withthe flow passage 27, which is between the end portion 21A and theprotruding portion 22E of the water lock 22, from the front via theopening 22H of the protruding portion 22E.

The cooling pipe 31 is connected to the engine 3 and the drain pipe 30.The watercraft body 2 includes a cooling passage which takes in waterfrom outside the watercraft body 2 and from the watercraft bottom ascooling water and feeds the water to the engine 3. Cooling water, whichpasses through the cooling passage and cools the engine 3, flows intothe flow passage 32 via the cooling pipe 31, passes the flow passage 32and the flow passage 27, and then flows into the inner space 22B of thecylindrical portion 22A of the water lock 22. Thus, the flow passage 32and the flow passage 27 guide the cooling water for the engine 3 fromthe cooling pipe 31 to the inner space 22B. At a joint between the drainpipe 30 and the protruding portion 22E, a rear end portion of the drainpipe 30 is securely connected to an outside surface of the protrudingportion 22E in the radial direction R. Thus, leakage of cooling waterfrom the joint between the drain pipe 30 and the protruding portion 22Eis significantly reduced or prevented.

The exhaust gas from the engine 3 flows in the upstream exhaust pipe 21and is guided to the end portion 21A. The exhaust gas which reaches theend portion 21A flows rearward along the pipe axis A in the end portion21A, as shown by a broken line arrow Y1.

The baffle 25 is located beyond the exhaust gas which flows rearward inthe end portion 21A. For example, the exhaust gas in the end portion 21Ais blocked by the baffle 25. The baffle 25 which is fastened to the endportion 21A by the bolts 26 blocks the exhaust gas which reaches the endportion 21A.

The exhaust gas in the end portion 21A cannot flow straight along thepipe axis A because the exhaust gas is blocked by the baffle 25. Thus,the exhaust gas changes flow direction to a cross direction Y2, whichintersects the pipe axis A, and passes the outlets 21D of the endportion 21A. The baffle 25 changes the flow direction of the exhaust gasin the end portion 21A to the cross direction Y2 at the outlets 21D byblocking the exhaust gas in the end portion 21A. Thus, the exhaust gasin the end portion 21A flows into the inner space 22B of the cylindricalportion 22A of the water lock 22 by being diffused radially outward inthe cross direction Y2 from the outlets 21D (FIG. 3).

The cross direction Y2 may be inclined rearward with respect to the pipeaxis A. In a preferred embodiment, a portion of an inner wall of thewater lock 22 that is parallel or substantially parallel with the pipeaxis A, for example, an inner wall 22J of the cylindrical portion 22A,is located beyond the exhaust gas which flows into the inner space 22Bfrom the outlets 21D. Thus, the exhaust gas which flows into the waterlock 22 flows rearward along the inner wall 22J, as shown by a brokenline arrow Y3.

The cross direction Y2 is preferably not only inclined with respect tothe pipe axis A but also extends along the inner wall 221 of the frontbaffle 22D which is perpendicular or substantially perpendicular to thepipe axis A, as shown by a broken line arrow Y4. In this preferredembodiment, the exhaust gas which flows into the inner space 22B flowsto the outside in the radial direction R along the inner wall 221, asshown by the broken line arrow Y4. The exhaust gas then flows rearwardalong the inner wall 22J of the cylindrical portion 22A as shown by thebroken line arrow Y3.

The exhaust gas flows rearward along the inner wall 22J of thecylindrical portion 22A. Thus, the occurrence of turbulence in the waterlock 22 is significantly reduced or prevented. For example, the exhaustgas in the water lock 22 reaches the inlet 23C of the downstream exhaustpipe 23 without being affected by the turbulence, refer to a broken linearrow Y5. The exhaust gas in the water lock 22 reaches the inlet 23Cafter flowing rearward along the inner wall 22J and flowing along aninner wall 22K of the rear baffle 22C. Alternatively, the exhaust gasreaches the inlet 23C while flowing along the inner wall 22J. Theexhaust gas which reaches the inlet 23C is exhausted to the outside ofthe watercraft body 2 from the exhaust port 2A (FIG. 1) after passingthe downstream exhaust pipe 23.

When the exhaust gas flows along the inner wall 22J of the water lock22, even if the exhaust gas is forceful due to high-speed rotation,acceleration, or deceleration of the engine 3, turbulence in the waterlock 22 is significantly reduced or prevented and exhaust efficiency isimproved.

Cooling water (shown by a dashed line arrow Y6) which flows into theinner space 22G of the water lock 22 from the flow passages 32 and 27 iscarried by the exhaust gas, as shown by the broken line arrows Y2 andY3, which is diffused in the cross direction Y2 from the outlets 21D andflows along the inner wall 22J of the water lock 22. For example, thecooling water reaches the downstream exhaust pipe 23, is mixed with theexhaust gas, and is drained to the outside of the watercraft body 2 fromthe downstream exhaust pipe 23. Thus, exhaust noise of the exhaust gasis significantly decreased or minimized compared to when only theexhaust gas is exhausted to the outside of the watercraft body 2.

Not only the exhaust gas, but also the cooling water flows along theinner wall 22J. Thus, not only exhaust gas exhaust efficiency but alsocooling water drainage efficiency are both improved. Moreover, becausethe turbulence of the exhaust gas in the water lock 22 is significantlyreduced or prevented, spray of the cooling water stirred by theturbulence in the water lock 22 is significantly reduced or prevented.Thus, spray reaching the engine 3 by flowing backward in the upstreamexhaust pipe 21 after infiltrating into the upstream exhaust pipe 21from the outlet 21D of the end portion 21A is significantly reduced orprevented. Since it is not necessary to account for a backward flow ofthe cooling water in the upstream exhaust pipe 21, a length of theupstream exhaust pipe 21 is reduced and a size of the exhaust system 20and the entire watercraft 1 is thus reduced.

Although a first preferred embodiment of the present invention has beendescribed above, the present invention is not restricted to the contentsof the first preferred embodiment and various modifications are possiblewithin the scope of the present invention.

Other Preferred Embodiments

FIG. 4 is a perspective view of the end portion 21A of the upstreamexhaust pipe 21 according to a first modification of a preferredembodiment of the present invention as seen from the rear. FIG. 5 is aperspective view of the end portion 21A of the upstream exhaust pipe 21according to a second modification of a preferred embodiment of thepresent invention as seen from the rear. FIG. 6 is a sectional view ofthe exhaust system 20 according to a third modification of a preferredembodiment of the present invention. Elements that are the same as thosedescribed above are identified in FIGS. 4, 5 and 6 by the same referencenumerals, and a description thereof will be omitted.

In the first modification shown in FIG. 4, the outlets 21D on the outerperipheral surface of the end portion 21A are omitted, and the baffle 25integrally and unitarily includes a cylindrical or substantiallycylindrical portion 25B (hereinafter, “cylindrical portion 25B”) whichextends forward from the outer periphery 25A. The cylindrical portion25B contacts the flange 21E from the rear. Thus, the baffle 25 isopposed to or covers the opening 21C of the end portion 21A at intervalsin the front-rear direction. For example, the opening 21C is not blockedby the baffle 25 and opens rearward. A plurality of notches 25C alignedin the circumferential direction S are disposed on the cylindricalportion 25B. Each notch 25C extends forward from a rear end of thecylindrical portion 25B and penetrates the cylindrical portion 25B inthe radial direction R. Each notch 25C is blocked from the front by theflange 21E and defines and functions as the outlet 21D. Each notch 25Ccommunicates with a gap, which is between the baffle 25 and the opening21C in the front-rear direction, from the outside in the radialdirection R.

In the first modification, the exhaust gas, which passes in the upstreamexhaust pipe 21 and is guided to the end portion 21A, flows rearwardalong the pipe axis A and passes through the opening 21C. The baffle 25is located downstream of the opening 21C. The exhaust gas is blocked bythe baffle 25 and changes its flow direction to the cross direction Y2which intersects the pipe axis A. The exhaust gas passes through eachnotch 25C and flows into the inner space 22B of the water lock 22 bybeing diffused outward in the radial direction R. The radially diffusedexhaust gas flows rearward along the inner wall 22J of the water lock22, as described above. Thus, the exhaust gas smoothly reaches thedownstream exhaust pipe 23 and is exhausted to the outside of thewatercraft body 2.

In the second modification shown in FIG. 5, the end portion 21A with theoutlets 21D and the baffle 25 are integrated by welding and the like,for example. Thus, the bolts 26 (FIG. 3) for fastening the baffle 25 tothe end portion 21A, and the bulge 21F to which the bolt 26 is installedare omitted. In a preferred embodiment, the outlets 21D are distributedequally or substantially equally in the circumferential direction S onthe outer peripheral surface of the end portion 21A. The end portion 21Ais fastened by, for example, bolts 35 to a portion of the upstreamexhaust pipe 21 that is located upstream of the end portion 21A.

In the third modification shown in FIG. 6, the water lock 22 includes apartition 40 and a relay pipe 41. The partition 40 preferably has acircular or substantially circular plate shape which is similar to therear baffle 22C of the water lock 22 and is located at a central orsubstantially central portion in the front-rear direction of the innerspace 22B of the water lock 22. The partition 40 divides the inner space22B into an upstream space 22L, which accommodates the end portion 21Aof the upstream exhaust pipe 21, and a downstream space 22M which islocated rearward relative to the upstream space 22L and accommodates theupstream end portion 23A of the downstream exhaust pipe 23. A drain hole40A is located at a lower end of the partition 40 to drain cooling watercollected in a lower portion of the upstream space 22L to the downstreamspace 22M.

The relay pipe 41 extends in the front-rear direction, is fixed to thepartition 40, and penetrates the partition 40 in the front-reardirection. In a preferred embodiment, the relay pipe 41 includes two ormore relay pipes 41, for example, and the two or more relay pipes 41 arealigned in the up-down direction, as shown in FIG. 6. The upstream space22L and the downstream space 22M communicate with each other via aninterior of the relay pipes 41. The exhaust gas which flows into theinner space 22B of the water lock 22 by being diffused radially outwardin the cross direction Y2 from the outlets 21D flows rearward along theinner wall 22J of the water lock 22 in the upstream space 22L (refer tothe broken line arrow Y3). The exhaust gas flows into the downstreamspace 22M via the interior of the relay pipes 41 and is exhausted to theoutside of the watercraft body 2 via the downstream exhaust pipe 23. Ina preferred embodiment, a taper 41A, which is enlarged in a forwarddirection, is located at a front end of the relay pipe 41. The exhaustgas in the upstream space 22L enters into the relay pipe 41 smoothly viathe taper 41A.

In a preferred embodiment of the present invention, instead of thebaffle 25, the flow direction diverter may include a guide 45, forexample, as shown by a broken line in FIG. 6. The guide 45 changes theflow direction of the exhaust gas in the end portion 21A to the crossdirection Y2. The guide 45 includes an inclined surface 45A disposed inthe end portion 21A. The inclined surface 45A is inclined with respectto the pipe axis A and extends outward in a rearward direction andradial direction R, and includes a tapered surface or a planar surface.The flow direction of the exhaust gas flowing straight along the pipeaxis A in the end portion 21A changes to the cross direction Y2 due tothe inclined surface 45A, such that the exhaust gas passes through theoutlets 21D of the end portion 21A.

In a preferred embodiment of the present invention, instead of the bolts26, the fastener may include a nut, for example, to fasten the baffle 25to the end portion 21A. The nut is installed, for example, on a screwshaft protruding rearward from the end portion 21A and penetrating thebaffle 25. The baffle 25 is thus fastened to the end portion 21A by thenut.

It is to be understood that features of two or more of the variouspreferred embodiments described above may be combined.

The present application claims priority to Japanese Patent ApplicationNo. 2016-150144 filed on Jul. 29, 2016 in the Japan Patent Office, andthe entire disclosure of which is incorporated herein by reference inits entirety.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,thus, is to be determined solely by the following claims.

What is claimed is:
 1. A watercraft comprising: a watercraft body; anengine in the watercraft body; an upstream exhaust pipe that includes anend portion with an outlet, and that guides exhaust gas from the engineto the end portion; a water lock that includes an inner space whichhouses the end portion and into which the exhaust gas flows from theoutlet; a downstream exhaust pipe that is connected to the water lock,and that exhausts the exhaust gas from the inner space to an outside ofthe watercraft body; and a flow direction diverter that changes a flowdirection of the exhaust gas at the outlet to a cross direction whichintersects a pipe axis of the end portion.
 2. The watercraft accordingto claim 1, wherein the end portion penetrates an inner wall of thewater lock, and the flow direction diverter changes the flow directionof the exhaust gas to a direction along the inner wall.
 3. Thewatercraft according to claim 1, wherein the outlet opens radially to anoutside of the upstream exhaust pipe at the end portion.
 4. Thewatercraft according to claim 1, wherein the flow direction diverterincludes a baffle that blocks the exhaust gas which reaches the endportion to change the flow direction of the exhaust gas.
 5. Thewatercraft according to claim 4, further comprising a fastener thatfastens the baffle to the end portion.
 6. The watercraft according toclaim 5, wherein the fastener includes three or more fasteners.
 7. Thewatercraft according to claim 1, further comprising a drain pipe thatsurrounds the end portion; wherein a flow passage defined between thedrain pipe and the end portion guides engine cooling water to the innerspace.
 8. An exhaust system for a watercraft with an engine, the exhaustsystem comprising: an upstream exhaust pipe that includes an end portionwith an outlet, and that guides exhaust gas from the engine to the endportion; a water lock that includes an inner space which houses the endportion and into which the exhaust gas flows from the outlet; adownstream exhaust pipe that is connected to the water lock, and thatexhausts the exhaust gas from the inner space to an outside of thewatercraft body; and a flow direction diverter that changes a flowdirection of the exhaust gas at the outlet to a cross direction whichintersects a pipe axis of the end portion.
 9. The exhaust system for awatercraft according to claim 8, wherein the end portion penetrates aninner wall of the water lock, and the flow direction diverter changesthe flow direction of the exhaust gas to a direction along the innerwall.
 10. The exhaust system for a watercraft according to claim 8,wherein the outlet opens radially to an outside of the upstream exhaustpipe at the end portion.
 11. The exhaust system for a watercraftaccording to claim 8, wherein the flow direction diverter includes abaffle that blocks the exhaust gas which reaches the end portion tochange the flow direction of the exhaust gas.
 12. The exhaust system fora watercraft according to claim 11, further comprising a fastener thatfastens the baffle to the end portion.
 13. The exhaust system for awatercraft according to claim 12, wherein the fastener includes three ormore fasteners.
 14. The exhaust system for a watercraft according toclaim 8, further comprising a drain pipe that surrounds the end portion;wherein a flow passage defined between the drain pipe and the endportion guides engine cooling water to the inner space.